package core.modules;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class EncryptionManager {

	private final static String HEX = "0123456789ABCDEF";

	public static String encrypt(String cleartext, String seed)  {
		
		
		try {
	        byte[] rawKey = getRawKey(seed.getBytes());
	        byte[] result = encrypt(rawKey, cleartext.getBytes());
	        return toHex(result);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}

	public static String decrypt(String encrypted, String seed) {
		
	
		try {
	        byte[] rawKey = getRawKey(seed.getBytes());
	        byte[] enc = toByte(encrypted);
	        byte[] result = decrypt(rawKey, enc);
	        return new String(result);
		} catch (Exception e) {
			return null;
		}
	}
	
	private static byte[] getRawKey(byte[] seed) throws Exception {
	        KeyGenerator kgen = KeyGenerator.getInstance("AES");
	        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
	        sr.setSeed(seed);
	    kgen.init(128, sr); // 192 and 256 bits may not be available
	    SecretKey skey = kgen.generateKey();
	    byte[] raw = skey.getEncoded();
	    return raw;
	}
	
	
	private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
	    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
	        Cipher cipher = Cipher.getInstance("AES");
	    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
	    byte[] encrypted = cipher.doFinal(clear);
	        return encrypted;
	}
	
	private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
	    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
	        Cipher cipher = Cipher.getInstance("AES");
	    cipher.init(Cipher.DECRYPT_MODE, skeySpec);
	    byte[] decrypted = cipher.doFinal(encrypted);
	        return decrypted;
	}
	
	public static String toHex(String txt) {
	        return toHex(txt.getBytes());
	}
	public static String fromHex(String hex) {
	        return new String(toByte(hex));
	}
	
	public static byte[] toByte(String hexString) {
	        int len = hexString.length()/2;
	        byte[] result = new byte[len];
	        for (int i = 0; i < len; i++)
	                result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
	        return result;
	}
	
	public static String toHex(byte[] buf) {
	        if (buf == null)
	                return "";
	        StringBuffer result = new StringBuffer(2*buf.length);
	        for (int i = 0; i < buf.length; i++) {
	                appendHex(result, buf[i]);
	        }
	        return result.toString();
	}
	private static void appendHex(StringBuffer sb, byte b) {
	        sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
	}
	
	
}
